Corrosion prevention method



United States Patent CORROSION PREVENTION METHOD Philip J. Raifsnider, Richmond, Califl, assignor to Shell Devlopment Company, Emeryville, Califi, -a corporawfion of Delaware No Drawing. Application April '14, 1953, Serial No. 348,811

11 Claims. .(CL- 252-855) lt-is an object of-the present invention to provide an inexpensive and industrially feasible method of corrosion inhibition-of fer-ruginousrnetals in a system in which-an .agitated flowing mixture of non-oxidizing gases, a liquelfied hydrocarbon-phase and an aqueous carbonic acid {phase come in contact with such ferruginous metal. Itis another object -.to overcome the disadvantages of prior art practices peculiar to corrosion inhibition as applied in operation .ofgas-condensate wells. A further object is .to 1

provide .an inexpensive and industrially feasible corrosion inhibition \treatment of iron-containing metals,contac tin g the above-specifiedtsystem as it occurs in the case of an operating gas-condensate well.

Now, in accordance with the present invention, it has ,been found .that corrosion which is caused by' contact of .corrodible metal With a system of non-oxidizing gases and .an agitated Ifio'wing mixture of a liquefied hydrocarbon phase and an aqueous carbonic acid phase .can be subsmut-11 ,inhibitedby introducing (continuously or intermittently) into this system a minor but corrosion-inhibiting amount of an oil-soluble acidic adduct of an alpha-- beta ethylenic polycarboxylic acid (including its anhydride') having not more than carbon atoms per mole- ,cule'fcombined with a non' hydroxylated polyunsaturated fatty acid'rafdica'l having from 8 to 32 carbon-atomsat an intermediate po'intin'the'carbon atom chain thereof.

r,- inaccordance with the presentinvention, fit found that additional improvements in corrosion inhibition may be obtained by combining the above oil- "soluble producflwith a water-soluble corrosion inhibitor whereby corrosion-due to both the aqueous and oil phases warns the oil "well are inhibited to an enhanced degree.

' The l'ique'fie'd hydrocarbon phase in gas-condensate wells normally comprises mixtures of liquid methane, anejpropanefbutane and heavier hydrocarbon conensate's -upto and including light gasolines havin g' up'to abort-"eight caibon atoms. Normally gaseous 'hydrocarnsare p'ar'tl'yjliquefie'd inthe well becauseof the preses ortlinarily existing therein. A typical gas-condensate "well produces between twenty and thirty-barrels of a liquefied hydrocarbon phase per million 'cubic feet of gas 1-(lVl'lY IOF), at itypical wellhead-temperatures and :pressures; The temperature's at theibottomof-the'wellzusually eriangedromabout 985 .C. :to about 125 (3., average temiiperat'ures eat the well-head being usually in thelrangev'frorn 'ra'hout C. 1;to -about-;80-1C. Pressurespintaqcondensate well usually range from about to about 7,000 pounds per square inch absolute. A typical well may have a bottom-holepressure of about 2,700 p. s. i. a. and a flowin'gtubing-pre'ssure of about 2,000 p. s. i. a. The pressure -ions orihigher'of liquid-water per MMCF of gas produced. 'This'liquid water phase dissolves-carbon dioxide,

--thus1providing the aqueous carbonic acid phase. The lat- --ter usually "has a pH value ranging from about 3.3 to about :a pHof 5.5. This aqueous phase may also contain sodium chloride and otherelectrolytes, the usual amounts of which are well known to the art. The aqueous car- .bonicac'id phase mixed .with agitated liquefiedhydro'car- .bon phase-and gases is usually distributed throughout-the fiowinglsystem off the well.

The above-defined zpolybasic acids or anhydrides are obtained .by the condensation of an alpha-beta ethylenic carboxy acid .or anhydride with a polyunsaturated, nonhydroxylated .fatty acid containing from eight to 332-car- .bon atoms,pr,eferably ten to twenty-four carbon atoms, -in itszcarbon chain. The desired-polybasic acid-or anhydride reactants may be prepared by .two different types .of reaction. .One .typeof reaction-involves the condensation of-an alpha-beta ethylenicacid or anhydride with .a conjugated, unsaturated, nonhydroxylatedfattyacid. The second typepfreaction involves thecondensation of an alpha beta ethylenic acid .of anhydride .with a non-conjugated, unsaturated, nonhydroxylated fatty-acid.

It is well known that maleic anhydride andotheralphabeta ethylenic acids or anhydrides will condense withconjugated, unsaturated fatty acids in accordance with Thieles theory of 1-4 addition. Thefatty-acid'in this case, of course must contain at least two carbon-tocarbo'n double bonds and thesemust be conjugated. This type of reaction has been thoroughly studied by Diels and co-workers, and is often referred to as .the Diels die'rie synthesis. The products are often calleddiene synthesis adducts.

Examples'of suitable fatty acids which will take part in a Diels condensation include: Geranic acid, elaeos'tearic acid, 10,12-octadecadienoic acid, tung oil fatty acids, etc. Actually, the esters of these acids, such as the triglycerides or'the esters of mono-, di-, or other poly- "hydric alcohols maybe employed in this condensation "in place of the fatty acid itself. Examples of suitable esters include: nrethyl-10,12-octadecadienoat, glycoldielaeostearate, oitacica oil, tung oil, dehydrated conjugated .castor oil, ethyl dehydrogeranate and the like. The osters (i. :e.,'glycerides of polyhydric alcohols may form ad- .ducts with the polybasic acid in'any proportion up to about one 'mol of the 'latter for each fattyacid radical. The rnost effective .adducts comprise those in which 'each estenmolecule contains at least one fatty acid radical in =adduct forr'n with the .polybasic acid.

The alpha-beta ethylenic carboxy acids or anhydrides which .are suitable for use in the aforementioned Diels ,diene synthesis'forpreparation.of the present productszare .thlosecontaining less'than ten carbon atomsand are exemrplified by=crotonic acid, maleic acid, fumaric acid, citraconic acid, glutaconic acid, acrylic acid, maleic'anhydride,

;and zcitraconic anhydride.

Polybasic acids or anhydrides contemplated :as reactants for production of .this new class of compounds ,arealso obtained by the condensation of an alpha-beta .,ethylenic acid, or anhydride with an unsaturated, non- .conjugated, non-.hydroxylated fatty acid containing from .ten to twenty-four carbon atoms in the ,carbon'chain. It ,has been shown by Clocker, U. S. Patents 2,188,882 to .2,= l- 8.8 ;89.2 inclusive, and .Bickford et ah, :Oil and .Soap,

. hydride.

February 1942, page 23 et seq, that such condensations may be brought about by heating the reactants at a suitable elevated temperature, usually above 200 C. and sometimes at temperatures above 300 C. The products formed are also acids or anhydrides, since the reaction does not appear to involve the destruction of these groups. The alpha-beta ethylenic acids or anhydrides which are suitable for use in the aforementioned condensation with nonconjugated, unsaturated, nonhydroxylated fatty acids are those containing less than ten carbon atoms and are exemplified by crotonic acid, maleic acid, fumaric acid, citraconic acid, glutaconic acid, acrylic acid, maleic anhydride, and citraconic an- Reference herein and in the claims to alphabeta unsaturated acids is intended to include the anhydrides corresponding to such acids. Actually they are recognized as being functionally equivalent in condensations of the kinds herein contemplated.

Suitable non-conjugated, unsaturated, non-hydroxylated fatty acids for use in condensation reactions with the above-mentioned alpha-beta ethylenic acids are those containing from ten to twenty-four carbon atoms in their carbon chains, and include undecylenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, etc.

Preferred condensation products are derived from a glyceride containing, in esterified form, a large proportion of non-conjugated, unsaturated, non-hydroxylated fatty acid. Examples of such glycerides are olive oil, corn oil, cottonseed oil, linseed oil, rapeseed oil, perilla oil, cranberry seed oil, menhaden oil, cod oil, whale oil, heat bodied linseed oil, etc.

It is not known just how the present class of inhibitors act to prevent corrosion of steel under the conditions employed in the present invention. Their effectiveness is surprising in view of the turbulence of flow in the system and the low concentrations of inhibitor (less than about 1 wt. percent, based on the liquefied hydrocarbon phase) which are effective, relative to the much higher concentrations of carbonic acid and other corroding components in the system. Also, these inhibitors are soluble in the liquefied hydrocarbon phase; so it would seem that they would be dissolved and swept away by the turbulent flow of this phase, leaving the surface of the metal open to attack by the swiftly churning aqueous carbonic acid present.

The present agents may be introduced into Wells in various ways. For example, tubing of relatively small diameter may be run down to the center of the production tube of such a well to approximately the bottom end thereof, and a solution of the present agent may be pumped through the small diameter tubing so asto enter thewell stream near the bottom of the well tube; the rising turbulent flow will then carry the injected agent up through the tube. Obviously, the corrosion inhibitors may be added or introduced into the wells by other means or methods depending, in part, on whether the wells are operated through the casings or through tubing disposed in such casings. Also, it is clear that the inhibitors may be introduced into the top of the well and allowed to flow down, or may be forced to any given point or points in the well, at which the inhibitor then can come in contact with the turbulent up-flowing fluid mixture which, as stated, would cause metal corrosion but for the presence of the corrosion inhibitors of this invention.

The employment of the present agents is best effected by having them in solution in a liquid hydrocarbon readily miscible with the liquefied hydrocarbon phase of the well system, and then introducing the hydrocarbon solution to a condensate well as above-described. Any organic solvent which is substantially non-reactive with the agent(s) under the conditions employed (e. g., such solvents as esters, alcohols, ketones, etc.), may be used for preparing an inhibitor solution, although it is preferable to employ light gasolines ornormally liquid or liquefied condensates from the well that is to be treated. In the alternative, 2. suitable crude oil or crude oil fraction (whether refined or not) is also eflicacious as a means of forming a fluid solution which can be flowed or forced into these condensate wells. In some cases it is advantageous to use a more or less concentrated solution or dispersion (up to about 50 wt. percent of the agent) in a suitable fluid medium such as diesel oil. The amount of solvent in the inhibitor solution is so small, relative to the volume of liquid in the system treated therewith, that it does not materially affect the normal operation of the well.

The subject adducts may be combined as noted hereinbefore with certain water-soluble corrosion inhibitors such as the alkali metal chromates or dichromates, e. g., sodium chromate; the alkali metal arsenites, e. g., potassium arsenite and the alkali metal phosphates, e. g., dipotassium hydrogen phosphate. By this means corrosion inhibitors are present in both the hydrocarbon phase and the water phase present in the well. Hence,..corrosion due to components contained in either one of these phases is substantially inhibited for a longer period of time.

In the operation of an oil well the oil is raised by pumping actionin which the sucker rods move against the sides of the well tubing. It will be apparent that the possibility for Wear is always present under such circumstances. In the past it has been common practice to replace tubing frequently during the replacement of corroded sucker rods. However, when the oil well is properly inhibited against corrosion of the sucker rods, the problem of tubing wear due to lack of proper lubrication between the sucker rods and the tubing becomes increasingly evident. In addition to the corrosion inhibiting function of the subject adducts the latter have been found to possess an unexpected benefit with respect to enhancing the lubrication of products being pumped through the oil well. This can be demonstrated by testing oil compositions with and without the subject adducts. A standard four-ball test is employed, the conditions being C., 7 kg. load and a speed of 600 R. P. M. The balls were one-half inch (diameter) SKF steel ball bearings having Rockwell C hardness of 60-65 Under these conditions the test oil, which was a lubricating oil having a SAE 10 viscosity, developed a scar diameter of 0.67 mm. Modification of the lubricating oil with 0.05% of the sardine oil adduct, whose preparation is described hereinafter, reduced the scar diameter to 0.43 mm.

Still further improvements in the lubrication benefits of the subject adducts may be made by sulfurising the same, using the well-known methods and agents for introducing sulfur and the extreme pressure agents and lubricants, such as sulfur, phosphorus sulfides or sulfur chlorides. It is preferred that the sulfur content of the resulting sulfurized adducts be between 0.5% and 10% by weight.

In providing the proper degree of corrosion resistant it is preferred that the adducts be present in the well in proportions between about 0.001% and 1% based on the hydrocarbon phase and still more preferably in amounts between 0.025% and 0.1%. 1

For the purpose of illustration, references will now be made to the following examples, it being understood that there is no intention of limiting the invention to the specific conditions and reactants disclosed therein. In these examples steel plates inch wide, 5 inches long, sand blasted cold rolled steel strips) were placed in fourounce cork stoppered oil sample bottles. Liquids saturated with carbon dioxide and having the following composition were added: 50 cc. of kerosene plus 10 cc. of distilled water containing 3% sodium chloride, 0.1% calcium chloride, 0.03% magnesium chloride and 0.1% acetic acid. The bottles were closed and rotated about 235 .C.

parts by weight of water and. washed with 200 .parts arcical-o end .over end at.60 R. P. M. for-.a period of 17-24 hours. The concentrationof .the=adducts given in the table below are based upon. the .kerosene weight. The testtemperature .was 180 F. ,At theend of this time-the corrosion ,rate was measured for each of =the steel plates. The results .of the above test technique are given .below.

Adducts were formed between maleicanhydride-and each one of the following oils: .crude oleic-acid,-sardine oil, linseed oil and soy bean oil. Jnrpreparing the adducts ,200 parts by weight of the oil were diluted with an equal weight of petroleum fuel oil to which20 parts by weight of maleic anhydride were added. The mixture .was heated .for 150 minutes at a temperature between about220-and The product washydrolyzed with 300 by weight of water. In order. to purify .the product it was then extracted with kerosene. Using the test method described above .the effectiveness .of eachof-the.individual inhibitors was found to be as follows:

I-claim as my invention:

L-The method of treating a hydrocarbomcontaining system in its natural state inaa -wellfor the'gpu'rpose of .inhibiting corrosion by aqueous carbonic .acid of well metal parts, said system comprising .a non-oxidizing gas phase, a liquefied normally .gaseous hydrocarbon :pha'se and a minor amountof .aqueous' carbonic-acid, which sys- .tem in-a state of agitated flow ata temperature of between about 45 C. and about 125 C. and underapressure of between about 100 and 7000 pounds per square .-inch absolute comes in contact with corrodible well parts, which method includes the step of mixing with--said;system an amount between about .001% and about 1% by weight of zthe hydrocarbon phase, :of anaci'dic adduct of an alpha-beta ethylenic polycarboxylic .acid having not more than carbon atoms per molecule, combined at an intermediate point in the carbon atom chain ofat least one non-hydroxylated polyethylenic fatty1 acid'r-adical, having from-8 to '32 carboh atoms, of a'fattyacid glyceride any ester radicals present in said adduct being glyceride radicals.

2. The method of treating a hydrocarbon-containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C. and under a pressure of between about 100 and 7000 pounds per square inch absolute, comes in contact with corrodible well parts,

system in-its natural state ina well for the purpose of inhibiting .corrosion by aqueous carbonic -.acid of well metal parts, said system comprising a; non-.oxidizingagas phase, aliquefied normally gaseous hydrocarbon phase and anminor amount' of aqueous carbonic acid, 'which system in'a state of agitated flow at a temperatureof =between-about C. and about 125 -.C. and under-a pressure of between about and 7000 ;poundsyper square inch absolute, comes rin-contact*with corrodible .well'parts, which method includes the step- 0f mixing with said system an amount-between about 0.001% and about 1% by weight of the hydrocarbon phase of an acidic adduct which is an alpha-beta ethylenic polycarboxylic acid, having not ,more than 10 carbonatoms' per molecule, combined at .an intermediate point in the carbon atom chain of at least one non-hydroxylated polyethylenic non-conjugated fatty acid radical, having-from 8 to 32 carbon atoms, of a fatty acid. glyceride anyrester radicals present in said adduct being glyceride radicals.

4. The method of treating a hydrocarbon-containing .system in its natural state in a well for-the purpose -10). inhibiting corrosion by aqueous carbonic acid of Well .metal ,parts, said system comprising a non-oxidizing'zgas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic-acid, which-system in a stateof agitated flow at atemperature of between about 45 C. and about .125 C. and under a pressure .of .betweenabout 100 and 7000 pounds ;persquare inch absolute comes in contact with corrodible well parts, which method includes the step of mixing with said .sysrtem anamount between about 0;001% and about 1%--b y weight of the hydrocarbon phase, of an acidic adduct-of .an alpha-beta ethylenic polycarboxylic acid having not more than 10 carbon atoms per molecule, combined at an intermediate point in .the carbon atom chain-of at least one-non-hydroxylated polyethylenic fatty vvacid rad- :ical, having from 12to 24 carbon atoms, of a fatty acid glyceride any ester radicals present in said adduct being ,glyceride radicals.

5. The method of treating a hydrocarbon-containing ,system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising -a non-oxidizing .gas phase, a liquefied-normally gaseous hydrocarbon phase and a minor amountof aqueous carbonicaoid,-'which system in a state of agitated .flow at ,a temperature of between about 45 C. and about C. and under a ,pressure of between about ":100wand-7000 pounds per square inch absolute, comes .in contact with corrodible well parts, which ,method includes the step-of mixing with said system anamount between about-0.001% :a-nd about 1% by weightof thehydrocarbon phase of sa :sulfurized acidic adduct of an alpha-beta ethylenic polycarboxylic acid having not more than 10 carbon atoms per molecule, combined at an intermediate point in the carbon atom chain of at least one non-hydroxylated polyethylenic fatty acid radical, having from 8 to 32 carbon atoms, of a fatty acid glyceride' any ester radicals present in said adduct being glyceride radicals.

6. The method of treating a hydrocarbon-containing system in its natural state in a wellfor the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C. and under a pressure of between about 100 and 7000 pounds per square inch absolute comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount between about 0.05% and about 0.25% by weight of the hydrocarbon phase, of an acidic adduct of an alpha-beta ethylenic polycarboxylic acid having not more than 10 carbon atoms per molecule, combined at an intermediate point in the carbon atom chain of at least one non-hydroxyl'ated polyethylenic fatty acid raditween about 45 C. and about 125 C. and under a pressure of between about 100 and 7000 pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount between about 001% and about l% by weight of the hydrocarbon phase of an acidic adduct of maleic anhydride combined at an intermediate point in the carbon atom chain of a non-hydroxylated polyethylenic fatty acid radical having from 8 to 32 carbon atoms any esterradicals present in said adduct being glyceride radicals.

8. The method of treating a hydrocarbon-containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C. and under a pressure of between about 100 and 7000 pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step off-mixing with said system an amount between about 001% and about 1% by weight of the hydrocarbon phase of an acidic adduct of an alpha-beta ethylenic polycarboxylic acid having no more than carbon atoms per molecule, combined at an intermediate point in the carbon atom chain of oleic acid any ester radicals present in said adduct being glycieride radicals.

absolute, comes in contact with corrodible well parts,

which method includes the step of mixing with said system an amount between about .001% and about 1% by weight of the hydrocarbon phase of an acidic adduct of an alpha-beta ethylenic polycarboxylic acid having no more than 10 carbon atoms per molecule,combined at an intermediate point in the carbon atom chain of at least one fatty acid radical per molecule of sardine oil glycerides any ester radicals present in said adduct being glyceride radicals.

10. The method of treating a hydrocarbon-containing system in its natural state in a Well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about C. and about 125 C. and under a pressure of between about and 7000 pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step] of mixing with said system an amount between about 0.001% and about 1% by weight of the hydrocarbon phase of an acidic adduct of an alpha-beta ethylenic polycarboxylic acid having no more than 10 carbon atoms per molecule, combined at an intermediate point in the carbon atom chain of at least one fatty acid radical per molecule of linseed oil glycerides any ester radicals present in said adduct being glyceride radicals.

11. The method of treating a hydrocarbon-containing system in its natural state in a well for the purpose of inhibitingcorrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase "and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about C. and under a pressure of between about 100 and 7000 pounds per square inch-absolute, comes in contact with corrodiblc well parts, which method includes the step of mixing with said system an amount betweenabout .001% and about 1% by weightof the hydrocarbon phase of an acidic adduct of an alpha-beta ethylenic polycarboxylic acid having not more than 10 carbon atoms per molecule, combined in an intermediate point in the carbon atom chain of at least one fatty acid radical per molecule of soybean oil glycerides any ester radicals present in said adduct being glyceride radicals.

References Cited in the file of this patent UNITED STAT ES, PATENTS 2,324,577 Haffner et a1. July 20, 1943 2,444,328 Blair June 29, 1948 2,614,983 Caldwell et al. p Oct. 21, 1952 

1. THE METHOD OF TREATING A HYDROCARBON-CONTAINING SYSTEM IN ITS NATURAL STATE IN A WELL FOR THE PURPOSE OF INHIBITING CORROSION BY AQUEOUS CARBONIC ACID OF WELL METAL PARTS, SAID SYSTEM COMPRISING A NON-OXIDIZING GAS PHASE, A LIQUEFIED NORMALLY GASEOUS HYDROCARBON PHASE AND A MINOR AMOUNT OF AQUEOUS CARBONIC ACID, WHICH SYSTEM IN A STATE OF AGITATED FLOW AT A TEMPERATURE OF BETWEEN ABOUT 45* C. AND ABOUT 125* C. AND UNDER A PRESSURE OF BETWEEN ABOUT 100 AND 7000 POUNDS PER SQUARE INCH ABSOLUTE COMES IN CONTACT WITH CORRODIBLE WELL PARTS, WHICH METHOD INCLUDES THE STEP OF MIXING WITH SAID SYSTEM AN AMOUNT BETWEEN ABOUT .001% AND ABOUT 1% BY WEIGHT OF THE HYDROCARBON PHASE, OF AN ACIDIC ADDUCT OF AN ALPHA-BETA ETHYLENIC POLYCARBOXYLIC ACID HAVING NOT MORE THAN 10 CARBON ATOMS PER MOLECULE, COMBINED AT AN INTERMEDIATE POINT IN THE CARBON ATOM CHAIN OF AT LEAST ONE NON-HYDROXYLATED POLYETHYLENIC FATTY ACID RADICAL, HAVING FROM 8 TO 32 CARBON ATOMS, OF A FATTY ACID GLYCERIDE ANY ESTER RADICALS PRESENT IN SAID ADDUCT BEING GLYCERIDE RADICALS. 